Producing soluble tanning agents.



UNITED STATES PATENT A OFFICE.

OTTO SCHMIDT, OF TLUDWIGSHAFEN-ONTI{E-RHINE, GER/M1 LNY, ASSIGNOR TOBADISCHE ANILIN & SODA FABRIK, OF LUDWIGSHAFEN-ON-THE- RHINE, GERMANY, ACORPCF PRODUCING SOLUBLE TANNING AG ENTS.

RATION.

j 216 612 Specification of Letters Patent.

No Drawing. Application filed July 2, 1914.

To all whom it may concern:

Be it known that I, O'r'ro Scimitar, citizen of the Geri'nan Empire,residmg at Ludwlgsliaten-on-the-lthme, Germany, have inwented new anduseful Improvements in Producing Soluble Tanning Agents, of which thefollowing is a. specification.

Several of the natural tanning agents, whether in the form of extract,or not, have the undesirable roperty of being either only difficultlysol iible, or insuiliciently soluble, in cold water; Thus, for instance,the

ingredients of the valuable quebracho extract which possess tanningproperties are, in a large proportion, insoluble, or difticultlysoluble.

I have found that such natural tanning extracts can be converted intoproducts which are readily soluble in cold water by treating them withan aromatic sulfonic acid of an amorphous character, which is free fromphenol, quinone and quinone-imid. groups, is soluble in water and iscapable of precipitating glue or gelatin from solutions thereof. Asparticular compounds which can be employed according to this invention,I mention the soluble condensation products obtainable from naphthalene,formaldehyde and sulfuric acid, which products are free from hydroxylgroups, but contain at least one sulfonic acid group. I mention,further; other products obtainable according to the specification of myapplication for patent, Serial No. 804,745, filed December at, 1013.

The process of my invention gives rise to products which are soluble incold water and are therefore eminently adapted for use in tanning. Thesaid process can be carried out either-by adding the said condensationproduct to the prepared tanning extract, or to the ditlicultly solubleparts thereof. Or it is equivalent to add'the said product to the thinsolution which is at first obtai'ned and then subsequently toconcentrate the treated solution. The mixtures can be effected, ormaintained, either at ordinary temperatures, or at raised, temperatures..ln some cases, the addition of the condensation product to thetanningextract tends to bleach the said extract, and this is a Furtheradvantage;

The following is an example of how in invention may be carried intopractical e i Patented Feb. 20, 1917.

Serial No. 841,664.

feet, but the i1". vention is not limited to this example. The parts areby Weight.

EmcmpZe,

.llcat togetlnr for about six hours at 150 (1., 10 parts ofmu'ihtl'lalcne and 10 parts of 97 per C(fl'lt s llflll'lti acid. Thencoolto about 80" (I. at the same time adding 2 parts of water, and hen,while maintaining this tQlTlPQIZltIH'Q, an id parts of 30 per cent.iorimildehyde solution and continue stirring until the odor offormaldehyde has disappeared. Then add caustic soda solution of 35 percent. ur til 10 grams of the product require, for con pleteneutralization, 10 cubic centimeters of :iormal caustic soda solution.Take 2000 parts of the paste thus obtained and introduce them slowly,while warming, into a hot mix ture of 2000 parts of solid quebrachoextr: ct with 2000 parts of Water. In this way, I. clear solution isobtained which can be diluted with water as required without becomiigdull, and which, after dilution, can be Cirectly used for tanning.

In a similar manner, solutions of other 'diilicultl y soluble extracts,such as mangrove and chestnut can be prepared, and other condensationprodt cts of the aforesaid type can be employed.

Now What I claim is 1. The process of conuerting diflicultly soluble oriusuticiently soluble tanning ex tracts into more soluble compounds btreat in; such dilticu tly soluble or insu ciently soluble extracts withan aromatic sulfonic acid of an amcrl'ihous character, which is Freifromphenol, quinone and quinone-imid groups, is soluble in water and iscapable of 3. The process of? converting ditficultly' soluble minsufiicicntly soluble tanning extracts into more soluble compounds btreating such dificultly soluble or insu ciently soluble extracts withthe product vobtainable from 10 parts of naphthalene, 10 my hand in thepresence of two subscribing parts of sulfuric acid, and 4.3 parts of 30witnesses. per cent. formaldehyde, which product is soluble in water,contains at least one sul- OTTO SCHMIDT.

5 fonie acid group, and is free from hydroxyl Witnesses:

groups. H. MERLE OOCHRAN- In testimony whereof I'have hereunto set J.ALEG LLOYD.

